[LLVMbugs] [Bug 15137] New: -fsanitize=address false positive in sscanf

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=15137

             Bug #: 15137
           Summary: -fsanitize=address false positive in sscanf
           Product: new-bugs
           Version: trunk
          Platform: PC
        OS/Version: Windows NT
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: new bugs
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: joerg.richter at pdv-fs.de
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified


cat > t.cc <<EOF
#include <cstdio>
int main()
{
  int d;
  char c;
  sscanf( "a12", "%c%d", &c, &d );
}
EOF
clang -o t t.cc -fsanitize=address
t

######

Gives:

=================================================================
==9879== ERROR: AddressSanitizer: stack-buffer-overflow on address
0x7ffffb5c2061 at pc 0x4113ec bp 0x7ffffb5c1ed0 sp 0x7ffffb5c1e60
...
Address 0x7ffffb5c2061 is located at offset 97 in frame <main> of T0's stack:
  This frame has 2 object(s):
    [32, 36) 'd'
    [96, 97) 'c'
...

>From [1]:

c
    Matches a sequence of bytes of the number specified by the field width (1
if no field width is present in the conversion specification). No null byte is
added. 

(Tested in trunk from 2013-01-25)

[1]: http://pubs.opengroup.org/onlinepubs/9699919799/functions/scanf.html

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